What Is Zoladex® (goserelin)?

Reviewed by: HU Medical Review Board | Last reviewed: June 2023

Zoladex® (goserelin) is a hormone therapy used to treat advanced breast cancer in both premenopausal and perimenopausal people with breast cancer that is hormone receptor-positive (HR+). It is also used to treat certain forms of prostate cancer and endometriosis.1-3

Goserelin is an implant that is injected under the skin. It slowly dissolves, releasing its medicine between doses.1-3

What is the ingredient in Zoladex?

The active ingredient in Zoladex is goserelin.1-3

How does goserelin work?

Many breast cancers are classified as HR+, meaning they have receptors on the surface of their cells where hormones like estrogen can attach. When the hormones connect with these receptors, they can fuel the growth of the cancer cells and lead to them growing and spreading.

Goserelin is a gonadotropin releasing hormone (GnRH) agonist. The pituitary gland secretes gonadotropin, which stimulates the production of estrogen by the ovaries. GnRH agonists like Goserelin stops the pituitary gland from releasing gonadotropin. This reduces the amount of estrogen in the body, which helps stop or slow the growth of breast cancer cells.1-3

What are the possible side effects?

The most common side effects of goserelin in breast cancer treatment include:1,3

Goserelin may also cause serious side effects, including:1-3

  • Temporary worsening of symptoms of breast cancer, including bone pain, during the first few weeks of treatment
  • High blood sugar levels
  • Heart problems, including heart attack and stroke
  • High levels of calcium in the blood (hypercalcemia)
  • Injury at the injection site
  • Allergic reaction
  • Depression

Tell your doctor if you have any new or worsening side effects while taking goserelin.

These are not all the possible side effects of goserelin. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with goserelin.

Other things to know

Goserelin should cause menstruation to stop. If your period continues, tell your doctor.1-3

Goserelin can harm an unborn baby. If you can become pregnant, you should use birth control during treatment and for some time after the last dose of goserelin. You should also not breastfeed during treatment with goserelin. Talk to your doctor about your options for birth control and breastfeeding while taking goserelin.1,3

Before beginning treatment for breast cancer, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

For more information, read the full prescribing information of goserelin.

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